Separated stable isotopes of carbon, nitrogen, and oxygen are presently produced by the Los Alamos Scientific Laboratory at the tens of kilograms per year level in a facility which is the world's largest and is the only one in the United States. The high production rate at sharply reduced costs has encouraged use of these isotopes in biomedical research and clinical studies. To expedite more general use of this new research tool, it is necessary to make labeled compounds more readily available to qualified investigators and, in many cases, to provide assistance in the analysis of experimental samples. We propose to continue the operation of a National, Stable isotopes Resource within the Los Alamos Scientific Laboratory, under the sponsorship of the National Institutes of Health (NIH), which will be responsive to the needs of the biomedical research community. The National Resource will continue to meet the needs cited above by: 1) Production of isotopes of carbon, nitrogen, and oxygen as required. 2) Synthesis of labeled compounds in response to requests by research workers according to priorities established by a national advisory committee. 3) Development of synthesis methods for compounds not now available. 4) Collaboration with qualified researchers in biomedical research which utilizes compounds with stable isotopes. 5) Operation of an educational program devoted to the effective production and use of stable isotope labeled compounds. 6) Support of core R&D at an appropriate level to improve and advance the above program.